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Патент USA US3082298

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March 19, 1963
0, B. PARKlNSON ET AL
3,082,291
HERMETIC SEAL
Filed Nov. 2, 1959
INVENTORS
DAVID B.PARKINSON
CLARENCE F. SPROSTY
ATT
United States
atent
F
"ice
3,082,291
Patented Mar. 19, 1963
1
2
3,082,291
cable. The conductor has an unwrapped portion extending
axially into the tubular anchor and into the inner cylinder.
HERMETIC SEAL
David B. Parkinson, Cleveland Heights, and Clarence F.
Sprosty, Parrna, Ohio, assignors to (Ilevite Corpora
tion, Cleveland, Ohio, a corporation of Ohio
Filed Nov. 2, 1959, Ser. No. 850,454
6 Claims. (Cl. 174—-77)
.A moisture resistant material is solidly packed within the
tubular anchor.
' For abetter understanding of the present invention,
together with other and further objects thereof, reference
is had to the following description taken in connection with
the accompanying drawings, and‘its scope will be pointed
This invention relates to an hermetic seal and more
out in the appended claims.
particularly to an apparatus and a method for hermeti 10 . In the drawing, the single FIGURE is a longitudinal
cally sealing a connection between electric conductors,
sectional view through an hermetic seal shown attached
the device being adapted'to prevent moisture molecules
from penetrating toward surfaces having critical electrical
to a housing.
free connection between an electric cable and a lead wire
part of an instrument not shown, for instance an accelerom
eter as. aforestated, having a lead wire 14 extending to
Referring to the drawing, the hermetic seal of this in
resistance characteristics.
vention is generally designated as 10'. It includes an ar
It is an object of this invention to provide a moisture 15 rangement in combination with a housing 12 which is
constituting part of a moisture sensitive device, for instance
accelerometers comprising piezoelectric transducing ele
ward the junction of housing 12 and seal 10‘. The housing
ments, as disclosed in co~pending application Serial
is substantially tubular and has an internal shoulder 16 on
Number 14,295 ?led March 11, 1960 and assigned to the 20 one end to rigidly receive a sealing member 20 therein.
same assignee as the present invention.
A conically tapered hollow extension 13 having a ribbed
It is a further object of this invention to provide an
surface is formed on the housing.‘ The sealing member
hermetic seal adapted to protect a given area to maintain
20 is adapted to engage an anchor device 30‘ which is
substantially the same degree of electrical resistivity over
secured to a cable 40‘.
a substantial period of time despite severe external climatic 25
The sealing member 20, preferably made of brass, has
conditions, for instance 95% humidity at tropical tem~
an internal bore 19 and a circumferential rim portion 21
peratures.
substantially circular in cross-section dimensioned for a
The present state of the art in missile components and
press ?t into the housing shoulder 16. A glass insulation
the like requires a high degree of accuracy and sensitivity.
bead 23 is sealingly mounted in bore 19 and the head has
More particularly, such instruments as piezoelectric ac 30 a central bore 24 to receive a rigid tubular member 25.
celerometers are drastically reduced in sensitivity where
The tubular member 25 is made out of a non-corrosive
penetration of moisture molecules into the unit occurs.
material such as stainless steel, or out of a suitable high
This causes enumerable problems because of the di?iculty
nickel alloy, and the member 2'5’ carries lead wire 14
to maintain a high degree of constant resistivity in the
from housing 12 and a lead wire 41 extending from elec
surrounding area where the lead wires are stripped of all 35 tric cable 40.
insulation. The order of magnitude in resistance herein
‘ Preferably, the abutting surfaces of the shoulder 16
considered is well beyond 100 megohms. While devices
and the peripheral portion 21 of the sealing member 20, '
of the prior art have been able to establish resistivity of
and particularly the edges adjacent thereto, are suitably
such magnitude, they have not been able to maintain a
soldered all around, or bonded together using epoxy
40
resistivity in the region of 300 megohms or higher for
cement or the like. The portion of the sealing member
extensive periods of time. For“ instance, devices in ac
20 facing the anchor device 30 has a radial receiving
cordance with the prior art when exposed to a humidity ‘ groove 22 to retain the anchor device 30 therein after the
environment of about 95% with temperatures ranging
unit has been assembled.
from 68° F. to 160° F. for a period of ten to ?fteen days
The anchor device 30 is made out of suitable rigid
or longer have consistently absorbed moisture molecules,
which in turn appreciably affected the degree of ‘resistivity
material and links the cable 40 to the sealing member 20.
reducing the same 10% or more. The present invention
has been subjected to tests indicating a constant resistivity
of 1000 megohms for seventeen days, at which time the
The ‘anchor device 39 is tubular, extending through it is
va longitudinal bore of non-uniform diameter consisting
of bore sections 32, 34 and 36; the bore diameter of the
individual sections being progressively larger toward the
tests were terminated. The tests indicated that the resist
location of the sealing member 20. At the location of the '
ance of the conducting parts surrounding the exposed lead
bore section 36 there is provided a wall section of suit
1 able thickness to ?t into the groove 22 of the sealing.
member 20. The center bore section 34 provides a cavity
wires did not vary more than a few ohms during and after
thetest period.
A major problem encountered is that of preventing the
substantially adjacent the end of the insulating glass bead
penetration of moisture molecules into the device and 55 23 and the tubular member 25; that is to say, the cavity
particularly along the “non-conducting” portions so as to
is de?ned at one end by the sealing member and at the
effect the resistivity by establishing a conducting ?lm of
opposite end by the bore section 32 which receives the
moisture along these “non~conducting” parts.
cable 40 snugly therein. The outside diameter of the
The present invention accomplishes this high degree
wall defining the bore section 32 is smaller than the out
of constant resistivity by providing an hermetically sealed
side diameter of the wall de?ning the bore section 34 to
electrical connection which includes a housing which has a
establish a longitudinal bore- 38 therebetween, the bore
central opening and a sealing member having an inner
.38 extending into the cavity and being adapted‘to receive
and an outer cylinder concentrically disposed with respect‘
a, closure plug 39 for reasons hereinafter ‘further ex
to each other. The outer cylinder is peripherally mounted
plained.
‘
within the opening of the housing and an intermediate.
‘To assemble the device the sealing member 20 is in
cylinder formed of non-conducting material is mounted
serted into the housing 12 and soldered thereto. Therebetween the inner and the outer cylinders. An electric
'after, cable 40 is suitably prepared, that is to say rubber
cable comprises a conductor enveloped by multiple outer
jacket 43 is pushed back from one end of the main cable
wrapping layers. Also provided is a tubular anchor mem
exposing 2 or 3 inches of braid 44. The amount of ex
70
ber, one end of the anchor member sealingly engaging the
posure varies with individual applications. Care must be
aforementioned outer cylinder and the opposite end of the
taken not to scuff or to crack the jacket in the process.
anchor member being interposed between layers of the
The tip 45 of the exposed braid 44 is cut off at an angle
-
3,082,291
d
of 45°, the ends of the braid are then smoothed down and
the anchor device 30 is slipped on and disposed under the
moisture proof substance with a hypodermic needle into
a cavity de?ned by the relatiye location of said anchor
jacket. A su?icient length of the wire tip is pulled out
and said wire; and applying a rubber-like molding com
pound around said seal assembly.
and exposed; and so is a Te?on insulation 47 which sur
rounds the Wire.
When "a low-noise ‘cable is utilized the
2. A method for making a seal ‘as described in claim 1,
Tei'lon is usually covered with graphite at its outer surface
wherein the hypodermic injection needle remains under
and the insulation is cut back as illustrated in the draw
pressure even while being removed ‘from said cavity.
ing. The exposed wires 41, 14 are polished and tinned in
’ 3. A method for making a seal adapted to hermetically
preparation for attachment.
protect a connection between a cable carrying an electric
To couple the wires the tinned portion of the wire 10 ?rst wire and a housing having therein a second wire,
41 is melted into the center opening 24 of the tubular
said housing having an opening therein which comprises.
terminal 25 alongside the wire 14 ‘from the housing 12.
the steps of: rigidly securing a sealing member having a
The tubular terminal is fully soldered and closed with tin.
tubular opening therethrough within said opening in. said“
housing, exposing a wire portion of said cable and insert-v
When thus prepared the anchor deviceStl is moved lon
gitudinally on the braid toward engagement position. with
ing it into said tubular opening, securing between layersv
the terminal groove 22 and secured thereto by cementing
of said cable an anchor device with said anchor device
being spaced away from the cable at the location of said
the circumferential portion of the anchor device at that
exposed wire portion to form a cavity, affixing said, ?rst
end with epoxy all around the anchor device and the ad
and; second wires wit in, said tubular opening and seal
jacent sealing member surfaces. The opposite end of the
anchor device 30 is then rigidly secured by soldering to 20 ing shut said‘ opening, suitably securing, said anchor de
vice to seal the space between said housing and said de
the braid 44. This serves to substantially relieve stresses
vice, ?lling said cavity with a moisture resistant substance,
in the cable 40 ahead of the electrical connection and
and thereafter molding moisture resistant material aroundv
accommodates the transfer of such stresses through the
the seal assembly._
rigid anchor device onto the housing 12. This arrange
4. A hermetically sealedv electrical connection com
ment prevents substantially any stress in the lead wire 41 25
prising, in combination; a housing having an; opening
which may be due on account of an external in?uence
therein; a sealing member having an inner and an outer
exerted on the cable 40. The bore 38 projecting into the
cylinder concentrically disposed with respect to each
cavity, formed: by bores 34 and 36, is used to load the
other, said outer cylinder being peripherally mounted,
cavity with a suitable moisture proof substance 27, for
instance grease, rubber, plastic, etc. The loading may be 30 within said opening, and an intermediate cylinderrformcd
of non~conducting material and mounted.v between: said
accomplished by utilizing a hypodermic needle which is
inserted into bore 38 to squirt the substance into the
cavity. After the cavity is entirely v?lled, the needle is
inner and outer cylinder; an electricalv cable comprising; a
conductor enveloped by multiple outer wrapping layers;
a tubular anchor member, one end of said anchor mem
removed while still applying pressure'to make sure that‘
the entrance portion of the bore 38 is also properly ?lled. 35 ber sealingly engaging said outer cylinder and the oppo
site cnds of the anchor member being interposed betweenv
A small tapered brass plug 39 is thereafter inserted into
said layers of said cable; said conductor having an un-.
the opening 38 with a press ?t, and preferably thereafter
.wrapped portion extending axially into said tubular an
the plug 39 is soldered to seal the opening.
chor and into said inner cylinder; and a moisture resist
The whole outside area is then thoroughly cleaned with
a primer in preparation for the application of a molded 40 ant material solidly packed within said tubular anchor.
5. A hermetically sealed electrical connection compris
rubber-like substance, the latter may be of a kind gen
ing, in combination; a housing having an inner bore; a
erally commercially available. The external portions of
sealing member having an inner and an outer cylinder
the subject device are carefully coated with bits of this
concentrically disposed. with respect to each other, said
rubber compound so as not to trap lair. Thereafter some
additional coating of this rubber-like material is placed 45 outer cylinder being peripherally mounted within said in
ner bore, and an intermediate cylinder formed of non
upon the assembly and a mold (not shown) is attached
conducting material and mounted'between said inner and.
thereto in the conventional manner with clamps holding
outer cylinder; an electrical cable comprising a conduc-.
the mold tightly in place. The assembly is then set to
tor‘ enveloped by multiple outer wrapping layers; a tu-v
dry. The drying condition depends of course on the type
bular anchor member having stepped. cylindrical walls,‘
50
of compound used.
one end of said anchor member sealingly engaging. said
While there have been described what are at present
outer cylinder and the opposite end of the anchor. mem
considered to be the preferred embodiments of this in
her being interposed between said layers of said'cable;
vention, it will be obvious to those skilled in the art that
said conductor having an unwrapped portion extending
various changes and modi?cations may be made therein
axially. into said tubular anchor and into said inner cylin
without departing from the invention. For example, the 65 der; a second conductor, the conductor being secured
invention may be utilized when connecting broken lines,
within the housing and extending into the inner cylinder
for instance telephone wires exposed to the weather. In
to electrically couple with the cable conductor; an elec
such an application a sealing member is of course not
trically conducting material within the inner cylinder
necessary. Similarly, the invention may be Worked with
substantially ?lling the latter; a moisture resistant mate-.
out the external rubber-like coat. It is therefore, aimed 60 rial solidly packed within said tubular anchor ‘excluding
in the appended claims to cover all such changes and
air bubbles, said material surrounding all portions of
modi?cations as fall within the true spirit and scope of
said unwrapped conductor within the anchor and the side
the invention.
surfaces of said sealing member adjacent to said anchor;
We claim as our invention:
and a rubber-like continuous coating surrounding por
11. A method for making a seal adapted to hermetically 65 tions of said housing, sealing member, anchor and said
protect a connection between a multiple layer cable carry
cable.
ing a wire and a housing having a wire therein, which
6. A hermetically sealed electrical connection compris
comprises the steps: of rigidly securing a sealing member
ing, in combination; a housing having an inner bore and
including a tubular member thereof into said housing;
providing
on one end a conically tapered hollow exten
exposing wire portions of said cable ‘for insertion into 70 sion; a sealing member having an inner and an outer
said tubular member; securing an anchor device between
cylinder concentrically disposed with respect to each
layers of said cable; tinning portions of said wires; solder
other, said outer cylinder being peripherally mounted
ing said wires into said tubular member; rigidly attaching
within said inner bore, and an intermediate cylinder
said anchor device to said sealing member; injecting a 75 formed of non-conducting material and mounted between. . .
3,082,291
5
6
said inner and outer cylinder; an electrical cable com
the anchor and the side surfaces of said sealing member
adjacent to said anchor; and a rubber-like continuous
coating having an inverse comically-tapered extension and
prising a conductor enveloped by multiple outer wrapping
layers; a tubular anchor member having stepped cylin
drical walls and forming a passageway for inserting a
compound therethrough, the passageway extending sub
stantially parallel with respect to the central axis of said
surrounding portions of said housing, the sealing mem
5 her, the anchor member and said cable.
tubular anchor, one end of said anchor member engag
ing said outer cylinder and the opposite end of the anchor
member being interposed between layers of said cable;
said conductor having an unwrapped portion extending 10
axially partly unwrapped into said tubular anchor and
into said inner cylinder; a second conductor secured with
in the housing and extending into the inner cylinder to
electrically connect with the cable conductor; electrically
conducting material within the inner cylinder substan 15
tially ?lling the latter; a moisture resistant material solidly
packed within said tubular anchor, said material sur—
rounding all portions or" said unwrapped conductor within
References Cited in the ?le of this patent
UNITED STATES PATENTS
1,888,075
Eby ________________ __ Nov. 15, 1932
1,977,808
Salisbury ____ _'.. ______ __ Oct. 23, 1934
2,292,358
2,697,739
2,876,322
2,886,626
Bishop ______________ __ Aug. 11,
Presswell ____________ __ Dec. 21,
Boggs _______________ __ Mar. 3,
Burnett ______________ __ May 12,
194-2
1954
1959
1959
FOREIGN PATENTS
726,054
608,042
France ______________ __ Feb. 23, 1932
Great Britain __________ __ Sept. 9, 1948
UNITED STATES PATENT OFFICE
CERTIFICATE OF CORRECTION
Patent No. 3,082,291
March 19 ,
1963
David B. Parkinson et 31.
It is hereby certified that error appears in the above numbered pet
ent requiring correction and that the said Letters Patent should read as
corrected below.
Column 4, line 9, for "a cable carrying an electric" read
—— an electric cable carrying a ——;
—-
end
line 36,
for "ends" read
——.
Signed and sealed this 3rd day of December, 1963.
(SEAL)
Attest:
ERNEST w‘
SWIDER
Attesting Officer
EDWIN L. REYNOLDS
AC 511%
Commissioner ut' Pah'nh
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